Among various batteries, a lithium battery having the advantages of light weight, high output and high energy density is frequently used as a power source of small-sized portable electronic equipment and portable information terminals, and supports the present information-oriented society. Also, a lithium battery has drawn attention as a power source of an electric automobile or a hybrid car, and further higher energy density, an improvement in safety, and upsizing are demanded therefrom.
Liquid electrolyte containing a flammable organic solvent is used for a presently commercialized lithium battery, so that the installation of a safety device for restraining temperature rise during a short circuit and the improvement in structure and material for preventing the short circuit are necessary therefor. On the contrary, a lithium battery all-solidified by replacing the liquid electrolyte with a solid electrolyte layer is conceived to intend the simplification of the safety device and be excellent in production cost and productivity for the reason that the flammable organic solvent is not used in the battery.
In the field of such an all solid lithium battery, it is known that the use of a sulfide solid electrolyte material for a solid electrolyte layer and an electrode layer improves Li ion conductivity of an all solid lithium battery.
On the other hand, the addition of a polymer as a binder to a solid electrolyte layer and an electrode layer is attempted. The addition of a polymer allows flexibility to the layers, and allows workability and moldability to be improved. For example, in Patent Literature 1, a solid electrolyte layer and an electrode layer, in which hydrogenated butadiene rubber (HBR) is used as a binder and 0.5Li2S-0.5P2S5 is used as a sulfide solid electrolyte material, are disclosed. Also, in Patent Literature 2, a binder for a hydrogen absorbing alloy electrode containing a hydrogenated block copolymer is disclosed.